The Fork of a Tree
Winter has taken a long time this year to leave us, but I think we have turned the corner now. Unfortunately, we are still looking at the mess winter has caused this year. During the bad storm at the beginning of March with the heavy snow and the fierce winds, we lost some trees. Although we had our woods logged only three years ago, this winter brought trees down that were considered “healthy” by the loggers. The late winter persistent rains and late snows saturated the ground and loosened the root systems’ grip on the ground. With partial thawing of the ground and then heavy snowfalls from two March nor’easters piling tons of weight on the trees, not much wind caused trees to come crashing down all over the region.
Indeed, as a result we lost power for six days (many in the region for several weeks!), when a 75 foot tall yellow pine became uprooted and hit our house, tearing off all electric service and damaging much more as well.
Indeed, as a result we lost power for six days (many in the region for several weeks!), when a 75 foot tall yellow pine became uprooted and hit our house, tearing off all electric service and damaging much more as well.
Surveying the damage, another tree caught my attention. It was a proud pine tree at the end of a grove of pines near the house, that seemed to be the pillar of the whole pine family. Interestingly, it still stands, despite losing half its mass. Viewed from a distance, it looked like a single tree. When we saw the ‘fallen tree’ beside it, from our den window, we at first couldn’t understand where it had come from, as this tree was the last one at the end of the grove and appeared to be still standing. But at a closer look, we noticed for the first time that while growing, it had formed a fork about 15 feet (5 meters) up, and only one of the leaders (new trunks) had come crashing down in the high winds. appearing to be a new tree
They had essentially become two distinct trees growing up another 60 feet (20 meters) tall from a single trunk. As the two leaders had stayed very close together and parallel to each other, each grew branches on only one side and, essentially became individually, badly unbalanced. With the added weight of snow on only one side and the high winds, the weakest point in the tree was the fork, and that is where one of them snapped.
The broken off leader has only branches on one side.
The two leaders were very close together. Notice all the debris at the break. So why did one leader break off and the other is still standing? Looking at the remaining stem, I can see that the tree is now totally unbalanced. It has only branches on one side of the remaining stem. On the other side it did not develop branches because, as it forked and formed a second stem, it did not have to grow branches on that side. And so, of course, the other leader did not grow branches on that other side, and this added to the reason the other leader broke off. The remaining leader is dangerous and needs to be removed. Even a slight wind may cause it to snap- it is no longer protected by the branches on the other side from wind, and with its sixty foot (20 meter) height, it can reach out and hurt somebody unexpectedly!
So what is forking and why does it happen? Is it- as most homeowners seem to believe, a defect that needs to be always pruned away, and does it occur naturally? Well the short answer is that there can be many reasons and they may not always need to be addressed.
It may be a naturally occurring fork, encoded in the species DNA, which adapted to certain types of climates or seasonal exposures to sun and environmental conditions. Or it could be the result of the local changing patterns of light or wind surrounding a tree as it grows in competition with surrounding plants or species. It could also result from accidental damage from deer browsing, birds, insects, frosts or droughts. Accidental forks seem to be the most unpredictable and most often in need of proper pruning. If the tree is important to you, you should definitely consult a trained arborist before trying to attempt any formation pruning! They can recognize the cause of the forking and whether or not the joint will continue to weaken or become stronger and effect the tree’s shape and stability over time.
So what is forking and why does it happen? Is it- as most homeowners seem to believe, a defect that needs to be always pruned away, and does it occur naturally? Well the short answer is that there can be many reasons and they may not always need to be addressed.
It may be a naturally occurring fork, encoded in the species DNA, which adapted to certain types of climates or seasonal exposures to sun and environmental conditions. Or it could be the result of the local changing patterns of light or wind surrounding a tree as it grows in competition with surrounding plants or species. It could also result from accidental damage from deer browsing, birds, insects, frosts or droughts. Accidental forks seem to be the most unpredictable and most often in need of proper pruning. If the tree is important to you, you should definitely consult a trained arborist before trying to attempt any formation pruning! They can recognize the cause of the forking and whether or not the joint will continue to weaken or become stronger and effect the tree’s shape and stability over time.
Bark inclusion into the fork of a broken ash leader
When a stem grows in two or more directions instead of one, they form forks. There are U-shaped and V-shaped forks. A U-shaped fork may form when a substantial branch of a tree turns up, trying to reach for light and space. If all the bark is visible in the crotch, the fork seems to be okay. With a V-shaped fork, things are different. Although one leader may be larger than the other- implying that it will turn into a dominant main trunk, it still will be a problem.
As both leads grow and thicken, the bark of each will disappear down into the fork from each side, and they will press against each other. (In fact, this ‘included patch’ of bark may become completely engulfed and invisible in an older fork, although the weakened joint remains.) You may not see this ‘bark inclusion’ again until the fork snaps or the tree is split for firewood.
Eventually the pressure between these opposing layers of bark will spread the fork and increase the splitting force. Under the bark, the living tissue will be crushed, which will then starve this area and destroy the tree’s defense system. Rainwater will seep into the fork, rot the bark and the wood, and eventually the weaker side of the fork will split from its own weight or under wind stress. Generally speaking, I’ve always been told that the more acute (narrow) the angle of the fork, the weaker and less reliable the bond.
As both leads grow and thicken, the bark of each will disappear down into the fork from each side, and they will press against each other. (In fact, this ‘included patch’ of bark may become completely engulfed and invisible in an older fork, although the weakened joint remains.) You may not see this ‘bark inclusion’ again until the fork snaps or the tree is split for firewood.
Eventually the pressure between these opposing layers of bark will spread the fork and increase the splitting force. Under the bark, the living tissue will be crushed, which will then starve this area and destroy the tree’s defense system. Rainwater will seep into the fork, rot the bark and the wood, and eventually the weaker side of the fork will split from its own weight or under wind stress. Generally speaking, I’ve always been told that the more acute (narrow) the angle of the fork, the weaker and less reliable the bond.
But it is very important to be able to recognize the different subtle structures of the fork before attempting to prune it. The architecture and properties of the various tissues of a tree are very complex. Some will produce antimicrobial materials and fungicides to ward off disease, others will form layers that will slowly cover wounds, some provide the plumbing that transports nutrients throughout the tree, while others will form the interlocking, torturous fibers that will give the fork its strength. (Picture the idyllic photo of a child on a swing hung from a thick horizontal tree branch or the ‘shade tree mechanic’ who parks his old car under a big shade tree and uses a big horizontal limb to hoist out the heavy engine of his car!) A trained arborist can recognize these features and place the cuts in the most successful locations.
Of course, you can strengthen the weaker branch of a fork with rods and cables, but this measure only postpones the failure. It will only get more dangerous with time to remove the now heavier, weaker part of a fork. The only good way to deal with such forks is to prune the weaker side while the tree is still young. Preventive pruning pays for itself many times over.
We had to cut some low hanging branches off our red maple tree some time ago. When I looked at those cuts now, after a couple of years, I was amazed how the tree was healing and was covering over those wounds. This way it has prevented fungal attacks to the tree and rot-infections. This is the tree’s defense against decay. If I hadn’t known to make the cuts just beyond the ‘branch collar’, I may well have destroyed the protective tissue that creates infectious material defenses, and then my tree would probably be already succumbing to fatal attacks.
Of course, you can strengthen the weaker branch of a fork with rods and cables, but this measure only postpones the failure. It will only get more dangerous with time to remove the now heavier, weaker part of a fork. The only good way to deal with such forks is to prune the weaker side while the tree is still young. Preventive pruning pays for itself many times over.
We had to cut some low hanging branches off our red maple tree some time ago. When I looked at those cuts now, after a couple of years, I was amazed how the tree was healing and was covering over those wounds. This way it has prevented fungal attacks to the tree and rot-infections. This is the tree’s defense against decay. If I hadn’t known to make the cuts just beyond the ‘branch collar’, I may well have destroyed the protective tissue that creates infectious material defenses, and then my tree would probably be already succumbing to fatal attacks.
Of course, I am looking at our trees with different eyes now, and found a few candidates that need more care in the near future. If preserving the beauty of your trees around your house, it isn’t enough of a prod to do preventative maintenance, then think of the costs in damage, inconvenience or injury! Of the two massive trees I mentioned that came down by our house, insurance only covered the one that hit our house! The removal of the other half broken tree and its still standing - and now dangerous remains - is not covered and will cost a lot of money to remove.
If you love trees, particularly near your house, you should take care of them. We always subscribed to the ‘let nature take its course’ philosophy. This is maybe not so great an idea when life and limbs are in play!
If you love trees, particularly near your house, you should take care of them. We always subscribed to the ‘let nature take its course’ philosophy. This is maybe not so great an idea when life and limbs are in play!
Several future vehicle accidents waiting to happen!
RSS Feed